Variable potentiometer



Oct. 13, 1964 R. ROOT VARIABLE POTENTIOMETER 2 Sheets-$heet 1 Filed May 15, 1963 [kill-l 5 u, a N N R m m W 1 w A 0 W W E z, 3Q M a p .3

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VARIABLE POTENTIOMETER Filed May 15, 1963 2 Sheets-Sheet 2 l/v VENTOR A24 swan 0C. A 007 .Ftq 3 A TTOXP/VEUS UnitedStates Patent 3,153,218 VARIABLE OTENTIQMETER Raymond C. Root, Columbus, Nolan, assignor to Dale Electronics, Inc, Columbus, Nehr. Filed May 15, 1963, Ser. No. 280,576 3 Claims. (Cl. 338-19ti) This invention relates generally to potentiometer structures and more particularly to variable potentiometers suitable for voltage division in electronic, electric, and electro-mechanical systems. It is an object of this invention to provide an improved potentiometer.

It is another object of this invention to provide a rotary potentiometer wherein the value of the resistance may be readily adjusted.

Another object of this invention is to provide a rotary potentiometer wherein a set of resistance elements arranged in parallel 'areradially spaced from another set of resistance elements arranged in parallel, and with said sets arranged in series with arcuately spaced terminals en gageable for eliminating either one set or both sets from the entire resistance value of the potentiometer, wherein the resistance value can be readily varied by rotation of a wiper arm.

A further object of this invention is to provide radially spaced sets of resistance elements connected with other sets arcuate spaced therefrom for providing a potentiometer the resistance value or" which is readily varied.

Yet another object of this invention is to provide an improved potentiometer having a non-conductive plate for supporting resistance elements thereon, and with electrical connections on both surfaces of the plate terminating for contact by a wiper arm on one face of the plate.

Still another object of this invention is to provide a rotary, variable potentiometer which is rugged, simple in construction, reliable, and easily and accurately assembled.

These objects, and other features and advantages of this invention will become readily apparent when taken into consideration with the accompanying drawings, wherein:

FIG. 1 is a partially exploded View of a preferred embodiment of the variable potentiometer of this invention;

FIG. 2 is a cross-sectional view of the potentiometer;

FIG. 3 is an enlarged plan View of the upper surface of the plate unit;

FIG. 4 is a fragmentary, perspective view of the plate unit, showing the resistance elements and portions of the circuit connections in dotted lines;

FIG. 5 is a reduced perspective view of the bottom of the plate unit; and

FIG. 6 is an enlarged, fragmentary vertical cross-sectional view showing a resistance element and electrical connections passing from the lower face of the plate unit to the upper face thereof.

Referring now tothe drawings, the variable potentiometer'of this invention is indicated generally at 10 in FIGS. 1 and 2. It comprises a case 11 of non-conductive material the lower half 12 of which is annular with a relatively flat bottom wall 13, an annular side wall 14, and having a circular chamber 16 formed within the side wall 14.

The upper half 17 of the case 11 is also annular and has a thickness substantially that of the bottom wall 13. It has a shoulder 18 which is adapted for a complementary fit with a shoulder 19 formed on the upper periphery of the lower half 12, and forming thereby agroove 21. To seal the two halves together, obviating thereby the entry of dust and other foreign particles into the chamber 16,,

a releasable retaining ring 22 is provided, the lower flange 23 of which extends into the groove 21.

- Within the, chamber 16 and supported in a stationary manner above the floor 24 of the bottom wall is a plate unit 26. T 1E plate unit includes a pair of identical, upper and lower non-conductive circular flat plates 27 and 28, respectively, arranged parallel to and vertically spaced from each other. Both plates 27 and 2% have circular openings 2? and 31 formed in their centers for passage therethrough of a rotatable shaft 32.

A resistance circuit is supported on the plate unit 24-, and comprises first a plurality of radially spaced sets of resistance elements and an electric circuit connecting these elements. As best viewed in FIG. 2, an inner set 33 of resistance elements includes a trio of radially aligned elements 33a, 33b, and 33c, and an outer set 3 of resistance elements includes a trio of radially aligned elements 34a, 34b, and 340. All six elements 3342-340 are radially aligned. Referring to FIG. 4, the inner and, outer sets of elements next to the sets 33 and 34, and arcuately spaced therefrom in a clockwise direction, are 35 and 3%, respectively, with sets 37 and 38, and 35 and 4% also being provided. Extended completely around the plates 27 and 23 are additional sets of radially spaced trios of resistance elements of predetermined values, with the last set 7 5' and 80 being arcuately spaced in a counter-clockwise direction from the next adjacent set 33 and 34.

Referring to, FIGS. 3 and 4, a straight circuit connection ll extends radially on the upper face lfi of the upper plate 27 from the outer edge 43 inwardly and is in electrical contact with upper common ends of the outer set 34 of resistance elements 34a, 34b and Radially spaced clockwise from the connection 41, and located approximately one-half the distance between the radially spaced and aligned sets 3-3 and 34, and 35 and 36, is another connection 44 extended inwardly on the upper face 42 from the outer edge The connection 44 (M63. 4 and 6) steps approximately at a point arcustely aligned with an outer resistance element 0, and is connected to a vertical connection dd which extends through both plates 27 and 28 to the lower surface 47 of plate 2 8.

Another connection 48 extends radially from the lowor end of connection 46 to contact the lower end of the outer resistance element 340. A further connection 49 extends radially inwardly on the lower face 47 of the plate 28 and is in electrical contact with the lower common endsof the outer set 34 of elements Eda, 34b, and 340, in addition to electrically connecting the lower common ends of the inner set 33 of elements 33a, 33b, and 33c.

Radially aligned with the connection 41 is another connection 51 which extends radially inwardly on the face 42 of the upper plate 2 7 to connect the uppercommon ends of the inner set 33 of resistance elements 33a, 33b, and 33c. The connection 51 includes a portion 52 which extends clockwise a short distance, another portion 53 which extends radially outwardly in alignment with the connection 44, another portion 54 extended clockwise a short distance, and another portion 41:: which extends radially outwardly to the edge 43 of the upper plate 2'3, electrically connecting the upper common ends of the outer set 36 of resistance elements 36a, 36b, and 360.

The upper common ends of the inner set 35 of elements are electrically connected by a connection 51a comparable with the connection 51, and having similar portions 52a, 53a, 54a, and 411'). Similarly, the lower common ends of the inner and outer sets 35 and 36 are electrically connected by a connection 29a, (FIG. 4) similar to the connection 4-9, and terminating via connection 4&1, 45m and on the upper surface 52 of the upper plate. It is readily seen that each adjacent pair of radially aligned and spaced sets of resistance elements are electrically connected in identical manners.

To impress a voltage across the circuit of the potention eter li a pair of terminal leads 61 and 62, extended through the case lit for external connection, are connected by conventional means to the first connection 41 (FIGS. 2 and 4), and to the last connection, 81 for example, respectively. For a purpose seen hereinafter, each connection, 41, 44, 41a, 44a, 41b, 44b, 41c, 44c, and 41v, 44v, and 81, are provided with dot-type circular terminals 63 on the face 42 of the upper plate 27.

Referring to FIG. 6, it is clearly illustrated that a connection 44-]: extends inwardly from the edge 43 of the upper plate 27 of engagement with a vertical connection 46, with a terminal 63 interposed in the connection 44k. The lower connection 48 from the connection 46 leads arcuately to the radial connection 49 which connects the lower end of the resistance element 56c with the common ends of the other elements of the set (not shown). On the upper surface 42, the connection 41k connects the upper end of the resistance element 560 with the other common ends. it is appreciated that each connection is connected to an end of a resistance element by a short lead 64 extended through a respective plate.

Referring to FlGS. l and 2, the shaft 32 is inserted through a bearing 66 mounted on the lower half 12.. The reduced upper end 67 of the shaft 37 is journaled within another bearing 68 mounted in the upper half 17 of the case 11, and with a portion 69 of the shaft 32 extended externally of the case 11 for rotation. A snap ring '71 or the like is secured to the shaft 32 and rotatable within a groove 72 provided in the lower half 12, to prevent longitudinal movement of the shaft 32.

Above the plate unit 26 is mounted a circular wiper arm 73 (FIGS. 1 and 2) of conductive material having a wiper element "1'4 formed on the periphery thereof and having a central opening 76 through which the shaft 32 extends. The wiper element 74 is engaged with the surface 42 of the upper plate 27, and is held thereagainst by a circular holder 77 of conductii e material. The wiper arm 73 is provided with a plurality of arcuately spaced tabs 78 adapted to be bent into locking engagement each with one of a plurality of notches 79 formed in arcuately spaced relation in the periphery of the holder 77.

The holder 77 has a central opening (not shown) for alignment with the wiper arm opening '76, and through which the shaft 32 extends. To mount the Wiper arm 73 and the holder 77 as a unit, a sleeve 81 is provided which is secured to the shaft 32 by any conventional means such as a lock nut 82, and which insulates the shaft from the arm 73 and holder 77.

Embracing the sleeve 81 for rotation therewith in response to rotation of the shaft 32 is an annular return member 83 of conductive material. The return member is engaged with the holder 77 so as to conduct electricity therefrom, and has a groove 84 formed in the upper end thereof. To transmit the return current from the return member 33, a collector unit (FIGS. 1 and 2) is provided.

The unit 86 includes a bolt terminal 87 both ends 33 and 19 of which are threaded, with a nut 93. threaded on the exterior end 18, and with a finger device 92 held on the interior end -39 by another nut @1. The finger device ")2 is U-shaped wherein the base 93 has an opening some d (not shown) through which the bolt 37 passes, and wherein a pair of flexible, parallel fingers 94 and 96 are adapted to and do frictionally engage the return member 83 within its groove In operation, upon engagement of the wiper arm 73 with the contact terminal 63 of connection 41 (FIG. 4), zero resistance is oifered by the circuit of the potentiometer lid. Upon movement of the wiper arm '73 in a clockwise direction to the terminal 63a, it is seen that the three resistance elements 34a, 34b and 340, arranged in parallel by the connections 41 and 49, are cut in, so to speak, to offer resistance in accord with their value. Putting it another way, their resistance value is cut out or eliminated from the overall resistance value of the entire potentiometer resistance circuit.

Upon further movement of the wiper arm 73 to 63b, it is seen that terminals 63 and 6312 are connected through the sets 34 and 33 of elements, arranged in series, by the main connections 41, 49, and 51. Thus, two sets of elements are cut in with respect to ofiering their resistance to current being passed from lead 61 to the Wiper arm 73, and outwardly through the collector unit 86. Further movement of the wiper arm 73 to the contact terminal 630 not only cuts in the sets 34 and 33, but also set 36 by means of the lower connection 4%, connected with the upper connection portion 41a via the resistance elements of the set 36.

It is therefore seen that upon each successive movement of the wiper arm 73, another set of resistances are cut into the resistance value offered, while simultaneously eliminating the set from the resistance value of the potcntiometer. it will be understood that the resistance value for any given set of elements may be varied, whereby the resistance eliminated may show a linear function or a non-linear function, depending on the predetermined resistance value or" each set.

In summation, a variable potentiometer has been described herein which is of a rotary type having a plurality of resistance elements arranged in parallel electrically and radially aligned physically with other elements with which the former elements are electrically in series, and wherein rotary movement of a wiper arm from one terminal to another selectively eliminates either one or both radially aligned sets of elements from the resistance of the potentiometer.

Some changes may be made in the construction and arrangement of my variable potentiometer without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim:

1. An adjustable potentiometer comprising in combination, a case having a chamber formed therein, a plate means mounted in said chamber, a plurality of pairs of resistance elements electrically connected to said plate, each pair of resistance elements being comprised of at least first and second sets of resistance elements, the resistance elements in each set being electrically connected in parallel, the sets of resistance elements in each pair being electrically connected in series, a plurality of spaced electrical terminals disposed in a circular path on said plate, pairs of adjacent terminals on said plate being electrically connected to opposite sides of said first set of resistance elements in one of said pairs of resistance elements, the second set of resistance elements in each pair being electrically connected in series to the first set of resistance elements in one next adjacent pair of resistance elements, electrical leads passing through said case and connected to at least two of said terminals, a shaft in said housing, a conductive arm on said shaft and adapted for operative movement over the path of said terminals to selectively effect an individual electrical contact with each of said terminals at different positions 0 5 of its movement, means secured to said arm for rotating outwardly from the center of the circular path defined said arm, and electrical means extending through said y Said r a case and being connected to said arm.

2. The device of claim 1, wherein said plate means is comprised of two parallel spaced apart plates, With 5 References Cited in the file of this patent UNITED STATES PATENTS v L 321,285 Doyle June 30, 1885 1sozlizgesresistance elements being disposed between said 607,540 Chase 3 1898 787,032 Goodall Apr. 11, 1905 3. The device of claim 1, whereln said plate means 1092 880 Weinand Apr. 14 1914 is comprised of two parallel spaced apart plates, with 10 1:475:667 1923 said resistance elements being disposed between said 1 33 ,0 9 g n 1 3 plates; said pairs of resistance elements extending radially 2,206,882 Davis July 9, 1940 

1. AN ADJUSTABLE POTENTIOMETER COMPRISING IN COMBINATION, A CASE HAVING A CHAMBER FORMED THEREIN, A PLATE MEANS MOUNTED IN SAID CHAMBER, A PLURALITY OF PAIRS OF RESISTANCE ELEMENTS ELECTICALLY CONNECTED TO SAID PLATE, EACH PAIR OF RESISTANCE ELEMENTS BEING COMPRISED OF AT LEAST FIRST AND SECOND SETS OF RESISTANCE ELEMENTS, THE RESISTANCE ELEMENTS IN EACH SET BEING ELECTRICALLY CONNECTED IN PARALLEL, THE SETS OF RESISTANCE ELEMENTS IN EACH PAIR BEING ELECTRICALLY CONNECTED IN SERIES, A PLURALITY OF SPACED ELECTRICAL TERMINALS DISPOSED IN A CIRCULAR PATH ON SAID PLATE, PAIRS OF ADJACENT TERMINALS ON SAID PLATE BEING ELECTRICALLY CONNECTED TO OPPOSITE SIDES OF SAID SET OF RESISTANCE ELEMENTS IN ONE OF SAID PAIRS OF RESISTANCE ELEMENTS, THE SECOND SET OF RESISTANCE ELEMENT IN EACH PAIR BEING ELECTRICALLY CONNECTED IN SERIES TO THE FIRST SET OF RESISTANCE ELEMENTS IN ONE NEXT ADJACENT PAIR OF RESISTANCE ELEMENTS, ELECTRICAL LEADS PASSING THROUGH SAID CASE AND CONNECTED TO AT LEAST TWO OF SAID TERMINALS, A SHAFT IN SAID HOUSING, A CONDUCTIVE ARM ON SAID SHAFT AND ADAPTED FOR OPERATIVE MOVEMENT OVER THE PATH OF SAID TERMINALS TO SELECTIVELY EFFECT AN INDIVIDUAL ELECTRICAL CONTACT WITH EACH OF SAID TERMINALS AT DIFFERENT POSITIONS OF ITS MOVEMENT, MEANS SECURED TO SAID ARM FOR ROTATING SAID ARM, AND ELECTRICAL MEANS EXTENDING THROUGH SAID CASE AND BEING CONNECTED TO SAID ARM. 